Acrylonitrile Butadiene Styrene (ABS) was first discovered during World War II when its basis, Styrene Butadiene Rubber (SBR), was used for alternatives to rubber. Commercially ABS polymers first became available in the early 1950s in an attempt to obtain the best properties of both polystyrene and styrene acrylonitrile.
ABS, however, has several disadvantages. ABS is (1) sensitive to thick sections in articles of manufacture which may cause voids, bubbles or sink; (2) susceptible to attack by hydrocarbons and other organic solvents; (3) exhibits low heat resistance and limited weather resistance; (4) relatively expensive to manufacture; and (5) is petroleum resource based.
There exists a need for materials, such as composite materials, that exhibit similar or improved mechanical properties, such as impact resistance and/or heat resistance, compared to neat ABS while being less expensive to manufacture, and from a resource base that is sustainable.
Numerous efforts have been made to increase the sustainability of traditional petroleum based polymers including blending with renewable resource based polymers. The preliminary research on ABS/PLA blends has showed poor performance due to incompatibility between the two. Several attempts have been made to increase the compatibility through the use of additives.
United States Patent Application No US/20120252977 describes a PLA composition in which PLA is modified with ABS and at least one compatibilizer selected from selected from the group consisting of: a poly (styrene-ethylene-butadiene-styrene) copolymer grafted with maleic anhydrides, an acrylonitrile-butadiene-styrene copolymer grafted with maleic anhydrides, a polystyrene grafted with maleic anhydrides, and an ethylene-ethyl acrylate-glycidyl methacrylate. In this application the PLA based blends include from about 34% to 47% by weight (wt. %) PLA, while the ABS can be anywhere from 15 wt. % to 70 wt. %. The highest impact strength alleged is 101 J/m with this system. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
European Patent Application No EP/2706090 describes a blended polymer system that contains polycarbonate (PC), ABS and PLA, and additives such as flame retardants and modified talc. Unfortunately, mechanical properties are not given for these blends, only crystallinity, heat distortion, and flame retardancy are investigated. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
European Patent Application No EP/2700678 describes a biodegradable polymer composite material comprising a biodegradable resin (PLA, polyhydroxybutarate, or polycaprolactone), ABS, and a reactive compatibilizer, such as glycidyl methacrylate, or maleic anhydride. Some improvement was seen relative to PLA properties, but only when high ABS amounts were used. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
United States Patent Application No US/20120220711 describes heat resistant PLA/ABS blends. The blends of this document include an oligomeric chain extender to increase adhesion, thereby increasing the heat distortion temperature. The blends may optionally include a stabilizer, an impact modifier and a filler. The blends do not include a lubricant, including an acrylic copolymer based lubricant. The best blend outlined in this document has an impact strength of 102 J/m with a heat distortion temperature of 98.1° C. According to this application, the PLA should be the “significant component”, meaning that PLA is present in at least thirty weight percent (30 wt. %) or more of the composition.
United States Patent Application No US 2012/0184672 describes the use of additives to increase the impact resistance and/or heat deflection temperature. The use of an oligomeric chain extender in addition to several other additives, such as plasticizer, fillers, impact modifier, and lubricant are employed. The PLA content in these blends is about 50 wt. % or more. The blends do not include ABS, or a lubricant, including an acrylic copolymer based lubricant.
Li et al., European Polymer Journal 45(3) 738-746 (2009) describes the use of styrene-acrylonitrile (SAN) grafted with glycidyl methacrylate (GMA), which is denoted SAN-GMA to act as an intermediary between the two phases. This paper describes a decrease in the size of the dispersed phase (ABS) upon reactive blending, which led to an increase in the toughness of the blend. This increase, however, was modest for the amount of additive that was used. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
Jo et al., Journal of Applied Polymer Science 125 (S2) 231-238 (2012) again attempts to use additives during blending to improve the performance of PLA/ABS blends. Although many different additives were attempted, the researchers showed that the best performance was attained with SAN-GMA in addition to a small amount of thermal stabilizer. However, a great deal of additive was used to achieve a modest improvement, their best blend being over 20 wt. % additive The blends do not include a lubricant, including an acrylic copolymer based lubricant.
Sun et al. Journal of Applied Polymer Science 122(5) 2992-2999 (2011) explains grafting GMA onto ABS before using it to toughen PLA. The improvement in the impact resistance achieved through this method was substantial. However, the method used to graft the GMA onto the ABS involved polymerizing the ABS from constituent monomers. This adds complexity and cost to the processing of such materials, decreasing their value and potential for use in commercial markets. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
Chevali et al. Polymer-Plastics Technology and Engineering 54 375-382 (2015) describes blending ABS with two natural fibers to form hybrid lignocellulosic biocomposites. With the inclusion of 20 wt. % fiber into the ABS matrix, impact resistance was reduced while the modulus was increased compared to neat ABS. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
Yeh et al. Composites Science and Technology 69 2225-2230 (2009) describes blending ABS with wood flour to form ABS based wood-plastic composites. The composites contained 50 wt. % wood fiber. With the use of coupling agents between the fiber and matrix, they were able to increase the properties of the composites compared to without coupling agent. The blends do not include a lubricant, including an acrylic copolymer based lubricant.
The art described above details blending of ABS with PLA and other bio-based plastics for increased sustainability. However, blends achieving performance similar to ABS has remained difficult to achieve.
There is a need for ABS based materials that incorporate some amount of bio-content to increase the sustainability of the material, and to exhibit performance values that are similar to ABS materials, and methods of making thereof.